For over 25 years, physicists predicted that shrinking certain semiconductor nanotubes to extreme dimensions would fundamentally alter their electronic behavior. The challenge was proving it, as structures at this scale are notoriously difficult to manufacture. Researchers at the University of Tokyo have now overcome that challenge by creating atomically precise molybdenum disulphide nanotubes measuring just one nanometre in diameter, approximately 100,000 times thinner than a human hair. This achievement resolves a long-standing theoretical question and provides a new platform for designing future ultra-miniaturised electronic components.
How Ultrathin Nanotubes Could Transform Transistors and Quantum Devices
Nanotubes have attracted scientific interest since the early 1990s due to their cylindrical atomic structures exhibiting unusual electrical, optical, and mechanical properties. While carbon nanotubes dominated research, scientists predicted inorganic semiconductor nanotubes could offer advantages for future electronics if atomic structures could be precisely controlled. In 1995, successful high-rate, gas-phase growth of MoS2 nested inorganic fullerenes and nanotubes was achieved.
Advancements in Functional Properties
Research shifted toward understanding unique physical properties: superconductivity in 2017 and enhanced intrinsic photovoltaic effect in tungsten disulfide nanotubes in 2019. Theoretical studies in 2000 and 2002 predicted that electronic properties and stability of MoS2 nanotubes would change significantly as diameters decreased, specifically predicting bandgap shrinkage.
The research 'Confined growth of armchair MoS2 nanotubes at the 1-nm limit' highlights the challenge of size. Conventional methods produce nanotubes larger than 10 nm, often with multiple walls and irregularities. Theoretical models suggested much smaller single-walled nanotubes should exhibit measurable bandgap changes, but those predictions remained untested until now.
Associate Professor Yusuke Nakanishi from the Department of Advanced Materials Science stated: "We achieved the synthesis of atomically precise semiconducting nanotubes with nanometer diameters. These precise nanotubes are identified as an ideal platform for nanoscale transistor channels." Measurements confirmed that the bandgap decreases with smaller diameter, directly confirming theoretical predictions from over 25 years ago.
Building a Stable Nanotube Only One Nanometre Wide
Researchers used boron nitride nanotubes as protective outer templates. Within these confined spaces, molybdenum disulphide atoms assembled into highly ordered single-walled nanotubes approximately one nanometre across. Historically, such small nanotubes were considered unstable due to extreme strain from high curvature. Stability was achieved using spatially confined reactions inside insulating boron nitride nanotubes.
Advanced electron microscopy and chemical mapping confirmed exceptionally well-defined atomic arrangements. The boron nitride acted as a stabilising shell, allowing ultrathin semiconductor nanotubes to form without collapsing. Unlike many existing systems with multiple concentric walls, the new architecture preserves a clean semiconducting channel with atomic-level precision.
Yusuke Nakanishi explained: "Their biggest advantage is atomic-level structural control. This specific architecture is viewed as a promising path toward creating truly nanoscale transistor channels."
Why the Discovery Matters for Future Electronics
As silicon transistors approach physical scaling limits, engineers explore alternative materials capable of maintaining predictable behaviour at extremely small dimensions. Tiny structural imperfections increasingly affect performance, creating major obstacles. The newly developed nanotubes offer a potential solution because their atomic structure can be controlled with far greater precision than conventional semiconductor channels.
The coaxial arrangement, with a semiconducting MoS2 nanotube surrounded by an insulating boron nitride nanotube, could be useful for gate-all-around transistor architectures, one of the most advanced designs pursued by the semiconductor industry. Although practical devices remain years away, the work establishes a new pathway for constructing semiconducting nanotubes with predictable electronic properties. The approach may extend to magnetic, superconducting, and other inorganic materials, broadening nanotube science beyond carbon-based systems.
More importantly, the achievement closes a chapter that began with theoretical calculations over 25 years ago. What was once a prediction confined to mathematical models can now be measured directly within a nanotube only one billionth of a metre wide.
